European Pat. No. 0 072 712 describes hydraulic assisted steering means for motor vehicles comprising a control shaft connected to the steering wheel and connected by a torsion bar to a follower shaft which carries a pinion engaged with the steering rack. Parts of the control shaft and of the follower shaft form the elements of a rotary distributor or valve which is inserted in the supply line of a hydraulic assist cylinder. When the driver exerts a torque on the steering wheel, the control shaft pivots resiliently with respect to the follower shaft so that the valve is actuated and sends fluid to the assisting cylinder so as to move the steering rack in the direction corresponding to the direction of rotation of the steering wheel.
Assisted steering means are also known in which the valve is a more reliable slide valve. But the use of a slide valve in the assisted steering known from the above European patent has technical problems, for it is difficult and complicated, in this assisted steering, to transform the relative angular movement of the two control and follower shafts into a translational movement of the valve.